The angle between the two vectors
`vec A = 3 hati + 4 hatj + 5 hatk , vec B = 3 hati + 4 hatj - 5 hatk ` is

Options

A. `90^(@)`
B. `"zero "^(@)`
C. `180^(@)`
D. `45 ^(@)`

Answer

A

Explanation

`vec A . vec B = ( 3 hati + 4 hatj + 5 hatk ) . ( 3 hati + 4 hatj - 5 hatk )`
`= 9 + 16 - 25 =0 implies A bot B.`